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AbstractPathogenic Escherichia colistrains on raw or insufficiently cooked foods are of public health concern as serious disease may result from their ingestion. Therefore, many commercial producers of beef products screen for E. coliO157:H7 before shipment. While Salmonellais not considered an adulterant on raw beef products, it is used as an indication of process control. To detect these microorganisms, rapid screening methods are often used to provide results within 8–24 hours after sampling. During 2005–2008, about 971,389 samples from several commercial beef production plants were tested using a rapid screening method based on the polymerase chain reaction to determine if they were presumptively positive for bacterial cells carrying Salmonellaor Shiga toxin–producing E. coli–specific genes. Of the product lots sampled (trim, ground beef, and variety meats), 15% were positive for the stx1and/or stx2(Shiga toxin genes), 9.1% for the eaegene (the attaching and effacing gene [eae] encoding intimin), 3.0% for an rfbgene region (encoding the O157-specific O side chain polysaccharide), and 1.67% for Salmonellaby the polymerase chain reaction assay. In general, lots of ground beef showed the lowest frequency of contamination, and variety meats (by-products of carcass evisceration), the highest. Overall, 4.6%, 4.6%, and 0.8% samples were screen-positive for enteropathogenic E. coli, enterohemorrhagic E. coli,and E. coliO157, respectively. Of the E. coliO157–positive samples, 14% were also Salmonellapositive. The frequency of screen-positive samples increases during the summer months, probably because of the prevalence of climatic conditions more conducive to microbial growth. The presence of fecal organisms in beef products suggests a failure of sanitary controls during processing and the more prevalent relatives of E. coliO157, Shiga toxin–producing Escherichia coli, enteropathogenic E. coli, and enterohemorrhagic E. coli, serve as more sensitive indicators of contamination than O157 strains alone.

ABSTRACTBacterial protein synthesis is the target for numerous natural and synthetic antibacterial agents. We have developed a poly(U) mRNA-directed aminoacylation/translation protein synthesis system composed of phenyl-tRNA synthetases, ribosomes, and ribosomal factors from Escherichia coli. This system, utilizing purified components, has been used for high-throughput screening of a small-molecule chemical library. We have identified a series of compounds that inhibit protein synthesis with 50% inhibitory concentrations (IC50s) ranging from 3 to 14 μM. This series of compounds all contained the same central scaffold composed of tetrahydropyrido[4,3-d]pyrimidin-4-ol (e.g., 4H-pyridopyrimidine). All analogs contained an orthopyridine ring attached to the central scaffold in the 2 position and either a five- or a six-member ring tethered to the 6-methylene nitrogen atom of the central scaffold. These compounds inhibited the growth of E. coli, Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis, with MICs ranging from 0.25 to 32 μg/ml. Macromolecular synthesis (MMS) assays with E. coliand S. aureusconfirmed that antibacterial activity resulted from specific inhibition of protein synthesis. Assays were developed for the steps performed by each component of the system in order to ascertain the target of the compounds, and the ribosome was found to be the site of inhibition.

The use of a DNA-based identification system (DNA barcoding) founded on the mitochondrial gene cytochrome coxidase subunit I (COI) was investigated for updating the U.S. Food and Drug Administration Regulatory Fish Encyclopedia(RFE; http://www.cfsan.fda.gov/~frf/rfe0.html). The RFE is a compilation of data used to identify fish species. It was compiled to help regulators identify species substitution that could result in potential adverse health consequences or could be a source of economic fraud. For each of many aquatic species commonly sold in the United States, the RFE includes high-resolution photographs of whole fish and their marketed product forms and species-specific biochemical patterns for authenticated fish species. These patterns currently include data from isoelectric focusing studies. In this article, we describe the generation of DNA barcodes for 172 individual authenticated fish representing 72 species from 27 families contained in the RFE. These barcode sequences can be used as an additional identification resource. In a blind study, 60 unknown fish muscle samples were barcoded, and the results were compared with the RFE barcode reference library. All 60 samples were correctly identified to species based on the barcoding data. Our study indicates that DNA barcoding can be a powerful tool for species identification and has broad potential applications.

Bacterial translation initiation factor IF2 is a GTP-binding protein that catalyzes binding of initiator fMet-tRNA in the ribosomal P site. The topographical localization of IF2 on the ribosomal subunits, a prerequisite for understanding the mechanism of initiation complex formation, has remained elusive. Here, we present a model for the positioning of IF2 in the 70S initiation complex as determined by cleavage of rRNA by the chemical nucleases Cu(II):1,10-orthophenanthroline and Fe(II):EDTA tethered to cysteine residues introduced into IF2. Two specific amino acids in the GII domain of IF2 are in proximity to helices H3, H4, H17, and H18 of 16S rRNA. Furthermore, the junction of the C-1 and C-2 domains is in proximity to H89 and the thiostrepton region of 23S rRNA. The docking is further constrained by the requisite proximity of the C-2 domain with P-site-bound tRNA and by the conserved GI domain of the IF2 with the large subunit's factor-binding center. Comparison of our present findings with previous data further suggests that the IF2 orientation on the 30S subunit changes during the transition from the 30S to 70S initiation complex.

The Food Safety and Inspection Service (FSIS) issued Pathogen Reduction; Hazard Analysis and Critical Control Point(HACCP) Systems; Final Rule(the PR/HACCP rule) on 25 July 1996. To verify that industry PR/HACCP systems are effective in controlling the contamination of raw meat and poultry products with human disease–causing bacteria, this rule sets product-specific Salmonellaperformance standards that must be met by slaughter establishments and establishments producing raw ground products. These performance standards are based on the prevalence of Salmonellaas determined from the FSIS's nationwide microbial baseline studies and are expressed in terms of the maximum number of Salmonella-positive samples that are allowed in a given sample set. From 26 January 1998 through 31 December 2000, federal inspectors collected 98,204 samples and 1,502 completed sample sets for Salmonellaanalysis from large, small, and very small establishments that produced at least one of seven raw meat and poultry products: broilers, market hogs, cows and bulls, steers and heifers, ground beef, ground chicken, and ground turkey. Salmonellaprevalence in most of the product categories was lower after the implementation of PR/HACCP than in pre-PR/HACCP baseline studies and surveys conducted by the FSIS. The results of 3 years of testing at establishments of all sizes combined show that >80% of the sample sets met the following Salmonellaprevalence performance standards: 20.0% for broilers, 8.7% for market hogs, 2.7% for cows and bulls, 1.0% for steers and heifers, 7.5% for ground beef, 44.6% for ground chicken, and 49.9% for ground turkey. The decreased Salmonellaprevalences may partly reflect industry improvements, such as improved process control, incorporation of antimicrobial interventions, and increased microbial-process control monitoring, in conjunction with PR/HACCP implementation.

The chemical nucleases 1,10-phenanthroline-Cu(II) and EDTA-Fe(II), have proven to be valuable tools for structural analysis of nucleic acids. Both have found applications in footprinting and directed proximity studies of DNA and RNA. Derivatives of each that provide for tethering to nucleic acid or protein are commercially available, allowing their widespread use for structural analysis of macromolecules. Although their applications are somewhat overlapping, differences in their cleavage mechanisms and chemical properties allow them to provide distinct and complementary structural information. The purpose of this study is to compare directly the cleavage patterns of tethered 1,10-phenanthroline-Cu(II) and EDTA-Fe(II) complexes within a similar experimental system. Here, the region surrounding nucleotide 1400 of 16S rRNA from Escherichia coliserves as a substrate for chemical cleavage directed by a derivatized complementary oligonucleotide. This region of rRNA is known to be involved in the decoding of mRNA during translation. The results of this study provide evidence in support of the mechanistic differences previously established for EDTA-Fe(II) and 1,10-phenathroline-Cu(II). The delocalized cleavage envelope produced by EDTA-Fe(II) cleavage suggests the involvement of a diffusible reactive species. On the other hand, rRNA cleavage induced by the tethered 1,10-phenanthroline-Cu(II) complex appears localized to the proximity of the chemical nuclease under normal conditions, although the production of an unknown diffusible species appears to occur during long reaction times.

The Food Safety and Inspection Service (FSIS) conducted microbiological testing programs for ready-to-eat (RTE) meat and poultry products produced at approximately 1,800 federally inspected establishments. All samples were collected at production facilities and not at retail. We report results here for the years 1990 through 1999. Prevalence data for Salmonella, Listeria monocytogenes, Escherichia coliO157:H7, or staphylococcal enterotoxins in nine different categories of RTE meat and poultry products are presented and discussed. The prevalence data have certain limitations that restrict statistical inferences, because these RTE product-testing programs are strictly regulatory in nature and not statistically designed. The cumulative 10-year Salmonellaprevalences were as follows: jerky, 0.31%; cooked, uncured poultry products, 0.10%; large-diameter cooked sausages, 0.07%; small-diameter cooked sausages, 0.20%; cooked beef, roast beef, and cooked corned beef, 0.22%; salads, spreads, and pâtés, 0.05%; and sliced ham and luncheon meat, 0.22%. The cumulative 3-year Salmonellaprevalence for dry and semidry fermented sausages was 1.43%. The cumulative 10-year L. monocytogenesprevalences were as follows: jerky, 0.52%; cooked, uncured poultry products, 2.12%; large-diameter cooked sausages, 1.31%; small-diameter cooked sausages, 3.56%; cooked beef, roast beef, and cooked corned beef, 3.09%; salads, spreads, and pâtés, 3.03%; and sliced ham and luncheon meat, 5.16%. The cumulative 3-year L. monocytogenesprevalence for dry and semidry fermented sausages was 3.25%. None of the RTE products tested for E. coliO157:H7 or staphylococcal enterotoxins was positive. Although FSIS and the industry have made progress in reducing pathogens in these products, additional efforts are ongoing to continually improve the safety of all RTE meat and poultry products manufactured in federally inspected establishments in the United States.

Chemical cleavage is developing into a powerful tool for analysis and characterization of nucleic acids. Phenanthroline-Cu(II) cleavage has been used extensively for studies of DNA for the last two decades, but recently has been applied to structural studies of RNA as well. This approach has been used to study the structure and structural changes occurring in ribosomal RNA within the ribosomes. In this article we discuss the mechanism by which phenanthroline cleaves, the applications possible using this approach, and the results that can be obtained. Protocols for use of phenanthroline are outlined as well.

Production of the thermostable direct hemolysin (TDH) by Vibrio parahaemolyticusis associated with pathogenicity of the organism and is encoded by the tdhgene. The timely resolution of seafood-associated outbreaks requires rapid and accurate detection of pathogenic V. parahaemolyticus. The specificity of alkaline phosphatase- and digoxigenin-labeled tdhgene probes was evaluated against 61 strains of V. parahaemolyticus(including isolates from recent outbreaks involving oysters from the Pacific Northwest, Texas, and New York), 85 strains of other vibrios, and 7 strains of non-vibrio species from clinical and environmental sources. The probes were specific for detection of the V. parahaemolyticustdhgene.

Short-term ultraviolet-B (UV-B) radiation was administered in the laboratory to mayfly nymphs (Diphetor hageni), midge larvae (Corynoneura taris), and snails (Elimia clavaeformis and Physella gyrina) to determine relative susceptibility of UV-B stress. Invertebrate response was a function of the total amount of UV-B received (dose, kJ m2), and the fluence rate at which UV-B was administered (irradiance, W / m2). Reciprocity did not hold for organisms tested in this study; effect of a given dose was dependent on irradiance. Invertebrates received a gradient of cumulative doses between 0 and 30 kJ / m2 UV-B while simultaneously receiving UV-A and photosynthetically active radiation. UV-B wavelengths were weighted with the DNA action spectrum to obtain biologically effective doses between 0 and 0.214 kJ / m2 UV-BDNA. This dose gradient was repeated at 3 different UV-B irradiances (1.6, 2.0, and 2.7 W / m2). Total dose, irradiance, and organism size all contributed to UV-B mortality. Mayfly nymphs and midge larvae had similar UV-B thresholds, and the lethal dose at which 50% of the organisms died (LD50) decreased with increased irradiance. For instance, LD50s for the midges were 17.2, 15.2, and 10 kJ / m2 at 1.6, 2.0, and 2.7 W / m2, respectively. Both snails were relatively resistant to UV-B. The prosobranch snail Elimia showed no mortality at any of the UV-B doses administered in this study. A size-class experiment using the pulmonate snail Physella suggested that organism size also affects its ability to cope with UV-B stress: small snails (1.2 ± 0.1 mm, $\overline{\text{x}}$ ± 1 SD) were 5 times more likely to die from UV-B exposure than medium (5.1 ± 0.3 mm) or large (7.8 ± 0.6 mm) snails. Our experiments demonstrated that benthic invertebrates are differentially susceptible to acute UV-B stress, which could lead to alterations in invertebrate assemblages where UV-B levels are high.

The effects of deoxyribonucleic acid (DNA) synthesis inhibition brought about in four different ways—thymidine starvation, nalidixic acid, hydroxyurea, and dnaBmutation—were examined in isogenic strains of Escherichia coliK-12. Three parameters were examined to determine whether there are strict correlations among them: (i) the extent of DNA synthesis inhibition; (ii) cell survival; and (iii) the rate of breakage of DNA molecules. There was no significant correlation between the extent of DNA synthesis inhibition and the rate of viability loss caused by the four DNA synthesis inhibitors, nor was there a strict correlation between the rate of occurrence of single-strand breaks in DNA and loss of viability. During treatment with hydroxyurea (0.1 M), no viability loss was observed and little, if any, single-strand breakage of DNA occurred. Both thymidine starvation and nalidixic-acid (20 μg/ml) treatment resulted in viability loss and breakage of DNA. For these latter two inhibitors, the two events appeared to be associated because greater rates of both viability loss and DNA breakage were observed for nalidixic acid compared with thymidine starvation. However, viability loss need not be associated with extensive breakage of DNA as demonstrated with a temperature-sensitive DNA synthesis mutant; at 39 C, viability loss occurred at a high rate without significant DNA breakage. With the other agents, the amount of DNA breakage accumulated when a cell population has sustained an average of one lethal hit was estimated to be about 30 single-strand breaks per genome. Differences in chromosomal and episomal breakage rates were observed.

Photosynthetic activity and nickel sorption by stream periphyton were examined in relation to light intensity. Ceramic tiles supporting moderate levels of periphyton were placed in laboratory microcosms and exposed to nickel ion and 14C-labeled sodium bicarbonate. Sorption of nickel increased hyperbolically as light intensity increased from zero to 300 µmol quanta m-2 s-1; this response was similar to the photosynthesis-irradiance relationship for periphyton collected from the same site. Nickel sorption with light was up to 76% greater than nickel sorption in the dark. Dark-related nickel sorption was likely attributable to sorption by hydrous iron and manganese oxides and to passive biotic sorption. These results suggest an important relationship between nickel sorption and photosynthesis, which may be a result of active uptake, adsorption through cation exchange, or nickel precipitation.

Faster methods for the detection of foodborne microbial pathogens are needed. The polymerase chain reaction (PCR) can amplify specific segments of DNA and is used to detect and identify bacterial genes responsible for causing diseases in humans. The major features and requirements for the PCR are described along with a number of important variations. A considerable number of PCR-based assays have been developed, but they have been applied most often to clinical and environmental samples and more rarely for the detection of foodborne microorganisms. Much of the difficulty in implementing PCR for the analysis of food samples lies in the problems encountered during the preparation of template DNAs from food matrices; a variety of approaches and considerations are examined. PCR methods developed for the detection and identification of particular bacteria, viruses, and parasites found in foods are described and discussed, and the major features of these reactions are summarized.

A high-power high-performance variable-speed drive system using a cycloconverter-fed synchronous motor is described. The control uses the field-orientation principle to give the drive system good steady-state and dynamic performance criteria. The accuracy of the field orientation is improved with the use of current regulators operating in the airgap flux reference frame. The system was manufactured to deliver 16 000 hp to the twin propeller shafts of a Canadian Coast Guard icebreaker. The electric components of the system were tested as a unit in the factory and the desired system performance was achieved.

Three Vibrio cholerae, [ill] isolates, pathogenic in both adult rabbit ligated ileal loop and infant rabbit assays, produced no heat-labile or heat-stable toxins. Their pathogenicity did not correlate with the presence of plasmids.

Tuskegee University's involvement with the sweetpotato was initiated in the late 19th century by Dr. George Washington Carver. Carver's publications on the sweetpotato include information on the history and varieties of sweetpotatoes, their cultivation, insect and fungal problems, and their treatment, harvesting, storing, canning, and preparation for human consumption and animal feed. Carver developed more than 200 products from the sweetpotato. Today sweetpotato research at Tuskegee University includes: biotechnology and genetic engineering, development of growing systems for long term space missions, health benefits and utilization of sweetpotato greens, effects of elevated carbon dioxide levels on sweetpotato growth and biochemistry, breeding new varieties, new food and non-food uses, new market niches, non-chemical pest control, modeling sweetpotato growth, sustainable cropping systems, degradation of foliage and roots to form sugars and ethanol, and use in international development. The National Sweetpotato Information Center (NSPIC) was established in 1993 with funding from USDA as a cooperative effort of Tuskegee University, the National Agricultural Library, and the University of Illinois. NSPIC goals include: materials collection; development of computer databases (materials, research and expert databases); digitization of full-text, non-copyrighted sweetpotato materials (using CD-ROM); teaching students and faculty to utilize NSPIC resources; and development of a network of people and institutions involved in sweetpotato research, production and utilization.

At natural densities in enclosures in an eastern Tennessee headwater stream, snails (Elimia clavaeformis) and juvenile creek chubs (Semotilus atromaculatus) affected benthic invertebrate assemblages. Elimia reduced the total number of invertebrates without affecting total invertebrate biomass. Conversely, creek chubs reduced the total biomass, but not the total number of invertebrates. No interaction was detected between snail and fish effects on either total invertebrate biomass or abundance. Both taxa appeared to affect the benthos by direct and indirect trophic pathways. Elimia reduced the abundance of non-tanypodine chironomids, apparently by interference. Elimia also appeared to reduce the abundances of some predators of benthic insects (salamanders [Desmognathus fuscus], dragonfly nymphs [Lanthus sp.], and young-of-the-year creek chubs). Juvenile creek chubs (55-70 mm total length [TL]) excluded young-of-the-year chubs (15-25 mm TL) from the enclosures and appeared to reduce the abundance of dragonfly nymphs. These changes may have increased the abundances of herbivorous/detritivorous insects such as the stonefly Leuctra. Multiple regression analyses indicated that snail and fish mass were more important than light in determining the total biomass and numbers of invertebrates in the channels.

The relationship of growth form to phosphorus uptake, carbon fixation, and susceptibility to grazing was tested in stream algae. We hypothesized that algal species with high surface area: volume (SA:V) ratios would have higher biomass-specific rates of nutrient uptake and photosynthesis than species with low SA:V ratios. We also predicted that algal species with gelatinous or prostrate growth forms would have low susceptibility to grazing. Physiological measurements were made using ten taxa comprising five different algal growth forms commonly found in flowing waters (unbranched filamentous; branched filamentous; gelatinous, branched filamentous; gelatinous, colonial; and prostrate). Significant positive relationships were obtained between SA:V and phosphorus uptake, and SA:V and carbon fixation at high light (200 µmol quanta m-2 s-1), but only after two outlying taxa were deleted from the analysis. A significant regression was obtained between SA:V and carbon fixation at low light (20 µmol quanta m-2 s-1) when all ten taxa were included. Herbivore preference for different growth forms was assessed in a short-term experiment which compared the amount of algae in snail feces vs. that on substrates. The ranking for least preferred to most preferred growth form was: gelatinous (colonial) = unbranched filamentous (Oedogonium) < prostrate < unbranched filamentous (Fragilaria). The overall results are consistent with the hypothesis that the functional attributes of lotic algae are related to their growth form. However, other factors beside growth form also can influence the functional performance and, by inference, the distribution of lotic algae in nature.

Current external criticism of American schooling includes an assumption that content textbooks used in upper grades fail to challenge the abilities of pupils. To investigate this assumption, the multiformula readabilities of 111 content textbooks currently employed in grades six through nine in 30 middle or junior high schools were obtained. Five and six formula, same sample readability data were collected and analyzed by 37 teacher researchers. Two or more formulas placed 49% of these texts one or more grade levels above grade of use. The results also were analyzed in light of current concerns about the accuracy and use of readability formulas. Readability placements varied notably and significantly between-texts and within-texts for each content area and grade level of use. Significant mean differences occurred in grade placement by formulas differing in comprehension criteria and in word count procedures. Extending sample selection from three to six and nine within-text samples did not change readability estimates notably or significantly. Teacher researcher procedural error occurred rarely. Teacher participants preferred the formulas combining realistic school estimates with efficiency in estimation.

Proponents of the theory of Protracted Social Conflict have given interesting narrative descriptions of some cases. We take a simplified version of the theory and apply it to South Africa. Using data from COPDAB we econometrically modeled conflict in South Africa from 1965 to 1981. We discover that conflict there is expected to remain protracted. (Keywords: South Africa, time series, econometric models)